Technical Field
This disclosure relates to printers that produce desired three-dimensional (3D) objects by fusing deposited powder, including 3D printers that use selective inhibition sintering (SIS).
Description of Related Art
Selective inhibition sintering (SIS) may be used to fabricate meso-scale polymeric and metallic parts. The fabrication may be in layers using loose powder as the initial material. Polymeric or metallic powder may be printed in thin layers. After each layer is printed, a liquid may be inkjet-printed on the layer in a pattern that defines the periphery of that layer, the interior portion of which may be a layer in a desired 3D object. The pattern for each layer may be derived from slices of a 3D CAD model of the object that is to be printed.
The liquid may include an agent that prevents powder particles of base polymer or metal that have been treated with the liquid from fusing with each other when heated. The infusible material may define an exterior surface of the desired 3D object. The fused material on both sides of the unfused material may then be easily separate from one another, thus allowing the desired 3D object to be readily isolated.
The fusible particles may be fused with heat (i.e., sintering). The sintering may take place after each layer is deposited, such as by passing a heat radiating device over each layer. All of the layers may instead be deposited, each with any needed inhibiting liquid, and the entire loose powder vat may then be sintered at the same time in a sintering furnace.
The inhibitor may be a salt solution which leaves particles of salt crystal in the inhibited regions after water evaporation. In case of polymeric part fabrication, these salt crystals may serve to separate the neighboring base polymer powder material particles and prevent them from fusing upon sintering. More details about this and related processes may be found in U.S. Pat. Nos. 6,589,471, 7,241,415, and 7,291,242.
Although SIS technology can be used to fabricate polymeric and metallic parts, in cases of very high temperature sintering it can be difficult to separate adjacent, uninhibited powder regions after they are sintered. Also, the vacuum that may exist when using 3D printing in space (e.g., on the moon and asteroids) may cause the fluid inhibitor to evaporate, preventing the fluid from inhibiting sintering of areas that are saturated with the fluid.